1. Field of the Invention
The present invention relates to an apparatus for controlling the filling amount of shredded tobacco in cigarettes so that the filling amount is fixed during the production the cigarettes.
2. Description of the Art
According to a cigarette production machine, shredded tobacco is fed onto a cigarette paper which travels in one direction. As the cigarette paper travels, the shredded tobacco is continuously wrapped in the paper, whereby a tobacco rod is formed. Thereafter, the tobacco rod is cut into individual cigarettes each having a predetermined length.
In order to improve the quality of the cigarettes as products, the filling amount of the shredded tobacco in each cigarette should be fixed in the first place. Accordingly, the cigarette production machine is provided with a control apparatus for controlling the filling amount of the shredded tobacco so that it is fixed. An example of this control apparatus is disclosed in Published Examined Japanese Patent Application No. 57-9353.
This conventional control apparatus includes a radiation-type density sensor, which continuously detects the filling amount of the shredded tobacco in the tobacco rod. In the control apparatus, an output from the density sensor is integrated for a given period of time by means of an integrator circuit, and the resulting integral value indicates the filling amount of the shredded tobacco corresponding to a predetermined length of the tobacco rod or a predetermined number of cigarettes.
Then, the control apparatus compares the calculated filling amount of the shredded tobacco with a reference value, and outputs a control signal which corresponds to the difference between the two values. This control signal is supplied to an adjusting device for adjusting the feed of the shredded tobacco onto the cigarette paper, thereby controlling the operation of the adjusting device. If the calculated filling amount of the shredded tobacco is smaller than the reference value, the adjusting device increases the feed of the shredded tobacco onto the paper. If the calculated filling amount of the shredded tobacco is greater than the reference value, on the other hand, the adjusting device reduces the tobacco feed. In this manner, the filling amount of the shredded tobacco for the predetermined length of the tobacco rod, that is, the filling amount of the shredded tobacco in the individual cigarettes, can be kept fixed.
Thus, the above-described control apparatus constitutes a section of the cigarette production machine which is essential to the stabilization of the cigarette quality.
As seen from the above description, the control apparatus computes the filling amount of the shredded tobacco corresponding to the predetermined number of cigarettes on the assumption that the length of the cigarettes, as well as the producing speed of the tobacco rod in the cigarette production machine, is fixed. Thus, the production machine is designed so as to produce fixed-length cigarettes at a constant speed. More specifically, a rod speed, which is represented by the product of the cigarette length and the rotational speed of the main shaft of the production machine, which determines the traveling speed of the cigarette paper or the tobacco rod, is constant.
Thus, the rod speed changes when manufacturing cigarettes of different lengths by means of one and the same cigarette production machine, or in the case where the rotational speed of the main shaft is changed to adjust the cigarette production. If the rod speed changes in this manner, the control apparatus cannot accurately compute the filling amount of the shredded tobacco to the predetermined number of cigarettes, and hence, cannot keep the filling amount of the shredded tobacco of each cigarette fixed.
If the rod speed is changed, therefore, the integrator circuit of the control apparatus requires adjustment. Entailing replacement of circuit elements, however, this adjustment cannot be made with ease.
Meanwhile, the rod speed cannot be constant during period between the reception of a starting signal by the cigarette production machine and the attainment of a given value by the rotating speed of the main shaft, or a period between the reception of an operation stop signal by the production machine and the full stoppage of the rotation of the main shaft.
Accordingly, the filling amount of the shredded tobacco cannot be accurately controlled with respect to the tobacco rod or cigarettes produced during those periods. Thus, these cigarettes are rejectable products which are excluded from management. If the rod speed of the cigarette production machine becomes higher, then the aforesaid periods are inevitably lengthened in proportion, so that the rejectable products increase.